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Yi Cui might just change the world. Last month the Stanford University professor of material science and his 50 strong team of researchers published a paper on the biggest battery breakthrough in decades – a self proclaimed ‘Holy Grail’. Now I speak to Cui to discover the real world practicalities behind what is potentially one of the most exciting scientific breakthroughs of recent times.

“It’s all about stabilizing lithium,” explains Cui, with understandable excitement in his voice. “When today’s Lithium Ion batteries are adapted to use lithium which remains stable in both the anode and electrolyte everything changes. The world can change.”

Cui is a man who talks fast, directly and on the move. While we talk he is preparing papers and heading back to the lab. There is the inescapable sense of a man on a mission.

Professor Yi Cui

And so there should be. Cui’s reference to ‘stabilizing lithium’ is a big deal. Lithium is a highly reactive substance, i.e., prone to overheating and catching fire.

To avoid such nasty issues, today’s lithium ion batteries combine a lithium electrolyte (which conducts electricity through the movement of ions) with a silicon or graphite anode (which sends the electricity into a device). If battery makers were able to use lithium in the anode itself, battery capacity would more than quadruple, and this is exactly what Cui’s team has pulled off.

“Our batteries have the same form factor as standard Lithium ion batteries,” says Cui. “From the outside they are identical to [the batteries we use today] the change is only on the inside.”

This is key. Pure lithium-anode batteries could be inserted straight into a remote control, phone or electric car. “You could have a cell phone with triple the battery life or an electric car with a range of 300 miles which can compete with an internal combustion engine,” claims Cui. “It changes how everything can be used.”

Pure lithium anode batteries have been made before, just not with the same success. Until now the best lithium-anode batteries have carried a 96% ‘Coulombic efficiency’ rating which means they lose 4% of their capacity with every charge as the lithium anode eats away the lithium electrolyte. They die after 25 full charging cycles.

Cui’s team has raised this efficiency to 99%, taking the charge cycles up to 100. Still, that's not enough for a commercial product. "The difference between 99 percent and 96 percent, in battery terms, is huge but the threshold for commercial viability is 99.9%,” says Cui. “While we're not quite to that 99.9% threshold, we're close.”

Coulombic Rating

How Cui and his researchers are solving this is by building ‘nanospheres’ – protective layers of interconnected carbon domes on top of the pure lithium anode. Lithium expands almost infinitely while charging, stretching out in wild hair-like structures which can warp, break or even cause the battery to explode.

The nanospheres stem this. Each layer has a honeycomb structure which is flexible, uniform and non-reactive which both stops the lithium ions expanding too much and the anode reacting with the electrode and generating excess heat. Remarkably the nanosphere barrier in each battery is just 20 nanometers thick – 1/5,000th the width of a human hair.

“With some additional engineering and new electrolytes, we believe we can realize a practical and stable lithium metal anode that could power the next generation of rechargeable batteries," says Cui.

Effect of carbon nanospheres

The pay-off in achieving this extra 0.9% is almost immeasurable because elsewhere there are virtually no downsides to this new battery structure. For starters Cui explains that pure lithium anode batteries charge just as fast as standard batteries, but given they have 3x the battery life in reality it is 3x as fast.

Furthermore Cui says this is just the start: “Where we are headed now is to speed it up and signs are it should be able to charge faster. I can certainly see it becoming a lot faster.”

Cost isn't a problem either. “At first there may be a small premium, but this type of tech will have a low cost pathway at least comparable to existing costs,” says Cui.

The reason for the professor's confidence is pure Lithium anode batteries don’t use any new resources – there is still lithium and carbon just in slightly different quantities and both are commodity materials. Cui even says the costs for pure lithium anode batteries may be lower than standard batteries over time as their greater efficiency means they store more energy from less electricity.

“From where I'm standing I can’t see price being an issue,” he concludes.

Yi Cui Research Team at Stanford University

Which leads to the biggest question on everyone's lips: when will these batteries be available? Cui is typically matter of fact: “Three years intense research and a commercial prototype in five years.”

In the last 13 years Cui has picked up 16 scholastic honours. If he and his team manage to commercialise the ‘holy grail’ battery, he can expect many more and they won't only be academic.